Gas hydrates along the northeastern Atlantic margin: possible hydrate-bound margin instabilities and possible release of methane

Mienert, J.; Posewang, Jörg; Baumann, Moritz

doi:10.1144/gsl.sp.1998.137.01.22

Cited by 100 publications

(78 citation statements)

References 32 publications

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“…The authors conclude that a geothermal gradient of 51.5 to 55.8°CÁkm -1 fits best the observed BSR at 250 to 300 mbsf in water depths ranging from 800 to 1250 m. Similar values around 55°C km -1 are reported by other authors as well (e.g. Mienert et al 1998;Andreassen et al 2003). However, there is a slight discrepancy between inferred geothermal gradients from the BSR depth, and the measurements stored in the HEAT database.…”

Section: The Age Of Crackssupporting

confidence: 83%

“…R/V Jan Mayen from Tromsø University) and hydrocarbon industry (BritSurvey 1999) revealed the presence of extensive bottom-simulating reflections (BSR) (e.g. Bugge 1983;Mienert et al 1998Mienert et al , 2001Mienert et al , 2005Bouriak et al 2000;Bünz et al 2003;Bünz and Mienert 2004;Hustoft et al 2007).…”

Section: S208mentioning

confidence: 99%

“…The northern flank of the Storegga area is further characterised by the presence of gas hydrates, shallow gas accumulations and fluid discharge features (e.g. Mienert et al 1998Mienert et al , 2001Bouriak et al 2000;Bünz et al 2003;Gravdal et al 2003;Hovland et al 2005). Widespread pockmarks and mounds have been associated with overpressured free gas below the gas hydrate stability zone (GHSZ) within the Plio-Pleistocene Naust Formation Hustoft et al 2007;Westbrook et al 2008;Hustoft et al 2009b, Bünz et al 2009Plaza Faverola et al 2010).…”

Section: Tectonic and Geological Settingmentioning

confidence: 99%

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Norwegian margin outer shelf cracking: a consequence of climate-induced gas hydrate dissociation?

Mienert

Vanneste

Haflidason

et al. 2010

Int J Earth Sci (Geol Rundsch)

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A series of en echelon cracks run nearly parallel to the outer shelf edge of the mid-Norwegian margin. The features can be followed in a *60-km-long and *5-km-wide zone in which up to 10-m-deep cracks developed in the seabed at 400-550 m water depth. The time of the seabed cracking has been dated to 7350 14 C years BP (8180 cal years BP), which corresponds with the main Storegga Slide event (8100 ± 250 cal. years BP). Reflection seismic data suggest that the cracks do not appear to result from deep-seated faults, but it cannot be ruled out completely that tension crevices were created in relation to past movements on the headwall of the Storegga slide. The cracking zone corresponds well to the zone where the base of the hydrate stability zone (BHSZ) outcrops. Evidence of fluid release in the BHSZ outcrop zone comes from an extensive pockmark field. We suggest that post-glacial ocean warming triggered the dissociation of gas hydrates while the interplay between dissociation, overpressure, and sediment fracturing on the outer shelf remains to be understood.

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Section: The Age Of Crackssupporting

confidence: 83%

Section: S208mentioning

confidence: 99%

Section: Tectonic and Geological Settingmentioning

confidence: 99%

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Norwegian margin outer shelf cracking: a consequence of climate-induced gas hydrate dissociation?

Mienert

Vanneste

Haflidason

et al. 2010

Int J Earth Sci (Geol Rundsch)

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“…These compounds are metastable and exist only under certain pressure and temperature conditions which exist naturally in deep marine sediments and in polar regions where permafrost is present. The estimated global volume of methane stored in hydrate ranges from 2 to 4 Â 10 16 m 3 at STP (temperature of 273.15 K and pressure of 101.325 kPa) [Kvenvolden, 1988] which, combined with its metastability, has led to hydrates becoming of international importance with regard to: their potential as a future energy resource [Collett and Ladd, 2000;Kvenvolden, 1998]; their role in global warming [Haq, 1998]; and their potential as a geotechnical hazard [Ashi, 1999;Berndt et al, 2002;Kayen and Lee, 1991;Mienert et al, 1998;Popenoe et al, 1993].…”

Section: Nature and Distribution Of Marine Gas Hydratesmentioning

confidence: 99%

A laboratory investigation into the seismic velocities of methane gas hydrate‐bearing sand

2005

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[1] Remote seismic methods, which measure the compressional wave (P wave) velocity (V p ) and shear wave (S wave) velocity (V s ), can be used to assess the distribution and concentration of marine gas hydrates in situ. However, interpreting seismic data requires an understanding of the seismic properties of hydrate-bearing sediments, which has proved problematic because of difficulties in recovering intact hydrate-bearing sediment samples and in performing valid laboratory tests. Therefore a dedicated gas hydrate resonant column (GHRC) was developed to allow pressure and temperature conditions suitable for hydrate formation to be applied to a specimen with subsequent measurement of both V p and V s made at frequencies and strains relevant to marine seismic investigations. Thirteen sand specimens containing differing amounts of evenly dispersed hydrate were tested. The results show a bipartite relationship between velocities and hydrate pore saturation, with a marked transition between 3 and 5% hydrate pore saturation for both V p and V s . This suggests that methane hydrate initially cements sand grain contacts then infills the pore space. These results show in detail for the first time, using a resonant column, how hydrate cementation affects elastic wave properties in quartz sand. This information is valuable for validating theoretical models relating seismic wave propagation in marine sediments to hydrate pore saturation.Citation: Priest, J. A., A. I. Best, and C. R. I. Clayton (2005), A laboratory investigation into the seismic velocities of methane gas hydrate-bearing sand,

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“…Miocene and older rocks have been documented beneath the Quaternary sections; these sequences have been exposed at places following erosion and/or tectonic uplift (Barnes et al, 2002;Field et al, 1997;Mountjoy and Barnes, 2011). Dissociation of gas hydrates has long been suspected to be involved in seafloor failure, mainly because of (1) "melting" of a potentially frame-supporting or cementing solid to water and (2) netvolume expansion leading to elevated pore pressure due to the generation of free gas (Kvenvolden, 1993;Mienert et al, 1998). Conversely, it has been implied that gas hydrate itself would strengthen sediments, as observed in a number of laboratory experiments (e.g., Priest et al, 2005;Winters et al, 2004).…”

Section: Geologic Setting Of Tuaheni Landslide Complexmentioning

confidence: 99%

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Barnes¹,

Pecher²,

LeVay³

2017

International Ocean Discovery Program Scientific Prospectus

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International Ocean Discovery Program (IODP) Expedition 372 combines two research topics, slow slip events (SSEs) on subduction faults and actively deforming gas hydrate-bearing landslides (Proposal 841-APL). Our study area on the Hikurangi margin east of New Zealand provides unique locations for addressing both research topics.Gas hydrates have long been suspected of being involved in seafloor failure; not much evidence, however, has been found to date for gas hydrate-related submarine landslides. Solid, icelike gas hydrate in sediment pores is generally thought to increase seafloor strength, as confirmed by a number of laboratory measurements. Dissociation of gas hydrate to water and overpressured gas, on the other hand, may destabilize the seafloor, potentially causing submarine landslides.The Tuaheni Landslide Complex on the Hikurangi margin shows evidence for active, creeping deformation. Intriguingly, the landward edge of creeping coincides with the pinchout of the base of gas hydrate stability (BGHS) on the seafloor. We therefore hypothesize that gas hydrate may be linked to creeping by (1) repeated small-scale sliding at the BGHS, in a variation of the conventional model linking gas hydrates and seafloor failure; (2) overpressure at the BGHS due to a permeability reduction linked to gas hydrates, which may lead to hydrofracturing, weakening the seafloor and allowing transmission of pressure into the gas hydrate stability zone; or (3) icelike viscous deformation of gas hydrates in sediment pores, similar to onshore rock glaciers. The latter two processes imply that gas hydrate itself is involved in creeping, constituting a paradigm shift in relating gas hydrates to submarine slope failure. Alternatively, creeping may not be related to gas hydrates but instead be caused by repeated pressure pulses or linked to earthquake-related liquefaction. We have devised a coring and logging program to test our hypotheses.SSEs at subduction zones are an enigmatic form of creeping fault behavior. At the northern Hikurangi subduction margin (HSM), they are among the best-documented and shallowest on Earth. They recur about every 2 y and may extend close to the trench, where clastic and pelagic sediments about 1.0-1.5 km thick overlie the subducting, seamount-studded Hikurangi Plateau. The northern HSM thus provides an excellent setting to use IODP capabilities to discern the mechanisms behind slow slip fault behavior, as proposed in IODP Proposal 781A-Full.The objectives of Proposal 781A-Full will be implemented across two related IODP expeditions, 372 and 375. Expedition 372 will undertake logging while drilling (LWD) at three sites targeting the upper plate (midslope basin, proposed Site HSM-01A), the frontal thrust (proposed Site HSM-18A), and the subducting section in the trench (proposed Site HSM-05A). Expedition 375 will undertake coring at the same sites, as well as an additional seamount site on the subducting plate, and implement the borehole observatory objectives. The data from each expedition will be...

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Gas hydrates along the northeastern Atlantic margin: possible hydrate-bound margin instabilities and possible release of methane

Cited by 100 publications

References 32 publications

Norwegian margin outer shelf cracking: a consequence of climate-induced gas hydrate dissociation?

Norwegian margin outer shelf cracking: a consequence of climate-induced gas hydrate dissociation?

A laboratory investigation into the seismic velocities of methane gas hydrate‐bearing sand

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